Obstructive airways disease with air trapping among firefighters exposed to World Trade Center dust

Abstract

Background: The World Trade Center (WTC) collapse produced a massive exposure to respirable particulates in New York City Fire Department (FDNY) rescue workers. This group had spirometry examinations pre-September 11, 2001, and post-September 11, 2001, demonstrating declines in lung function with parallel declines in FEV(1) and FVC. To date, the underlying pathophysiologic cause for this has been open to question.

Methods: Of 13,234 participants in the FDNY-WTC Monitoring Program, 1,720 (13%) were referred for pulmonary subspecialty evaluation at a single institution. Evaluation included 919 full pulmonary function tests, 1,219 methacholine challenge tests, and 982 high-resolution chest CT scans.

Results: At pulmonary evaluation (median 34 months post-September 11, 2001), median values were FEV(1) 93% predicted (interquartile range [IQR], 83%-101%), FVC 98% predicted (IQR, 89%-106%), and FEV(1)/FVC 0.78 (IQR, 0.72-0.82). The residual volume (RV) was 123% predicted (IQR, 106%-147%) with nearly all participants having normal total lung capacity, functional residual capacity, and diffusing capacity of carbon monoxide. Also, 1,051/1,720 (59%) had obstructive airways disease based on at least one of the following: FEV(1)/FVC, bronchodilator responsiveness, hyperreactivity, or elevated RV. After adjusting for age, gender, race, height and weight, and tobacco use, the decline in FEV(1) post-September 11, 2001, was significantly correlated with increased RV percent predicted (P < .0001), increased bronchodilator responsiveness (P < .0001), and increased hyperreactivity (P = .0056). CT scans demonstrated bronchial wall thickening that was significantly associated with the decline in FEV(1) post-September 11, 2001 (P = .024), increases in hyperreactivity (P < .0001), and increases in RV (P < .0001). Few had evidence for interstitial disease.

Conclusions: Airways obstruction was the predominant physiologic finding underlying the reduction in lung function post-September 11, 2001, in FDNY WTC rescue workers presenting for pulmonary evaluation.

Figure 1.

Schematic representation of those receiving pulmonary evaluation and further diagnostic testing. FDNY = New York City Fire Department; MCT = methacholine challenge testing; PFT = pulmonary function test; WTC = World Trade Center.

Figure 2.

Proportion of exposed FDNY rescue workers presenting for pulmonary evaluation. The number (percent) of each exposure category presenting for evaluation differed significantly (P = .0001); 1,720/13,234 (13%) of the total population, 404/2,152 (19%) of those in the high-intensity exposure category, 1,230/9,680 (13%) of those in the intermediate-exposure category (Inter), and 86/1,402 (6%) of those in the low-exposure category received subspecialty evaluation. The total number of individuals in each group is shown in parentheses below the group label. The error bars show the 95% CIs. See Figure 1 legend for expansion of abbreviation.

Figure 3.

Correlation of decline in FEV₁ post-September 11, 2001, with other physiologic measures of airway injury. After adjusting for age, gender, race, height and weight (or BMI instead of height and weight), and tobacco-smoking status, the post-September 11, 2001, decline in FEV₁, calculated as the %FEV₁ post-September 11, 2001,/%FEV₁ pre-September 11, 2001, correlates with bronchodilator response (P<.0001; r² = 0.29) (A) and RV% predicted (P<.0001; r² = 0.14) (B). BD = bronchodilator; RV = residual volume. See Figure 1 legend for expansion of other abbreviations.

Figure 4.

Correlation of BWT on CT scan with measures of airway injury. The presence of BWT is associated with air trapping as measured by elevated RV percent (P < .0001) (A); FEV₁ decline in the interval from the pre-September 11, 2001, spirometry to the post-September 11, 2001, measurement at the time of the pulmonary evaluation as calculated from the difference between percent predicted values (P = .0024) (B); and airway reactivity as measured by methacholine challenge slope (L/mg) (P < .0001) (C). BWT = bronchial wall thickening. See Figures 1 and 3 legends for expansion of other abbreviations.